In electrically operated devices such as roller shutters, rolling gates, jalousies, awnings, movie screens, etc., the conventional way of setting the desired end positions is to use adjustable mechanical limit stop switching devices. Examples of drives of this type are known from DE No. 3,011,706 C2 and DE No. 4,402,524 C2. In these known drives, the drive shaft of the drive is stopped in an upper and lower end position by means of so-called shaft limit switches. So that shaft limit switches of this type can be adjusted, the switch usually has setting buttons, by means of which the relative position of cam wheels inside the shaft limit switch can be reset. So that the lower end position can be adjusted, the roller shutter, etc., must first be rolled down, and just before it reaches the desired lower end position, the set button responsible for shutting off the motor must be pushed. A similar process is used to set the upper end position of the jalousie.
Shaft limit switches of this type are relatively complicated in their design, and, depending on the location where they are installed, it can often be difficult to adjust them because of difficulty of access. In addition, these known shaft limit switches are unable to protect the roller shutters, etc., from damage as they are rolled up and down. That is, if the roller shutter becomes jammed or blocked as it is rolled up or down, the known shaft limit switches do not shut off the drive because these switches are designed only to turn the drive off at the end position. The drive therefore continues to run and can therefore damage the component being driven and even, in an extreme case, destroy it.
Another problem is the possibility that ice can form on the roller shutter, etc., to be actuated, wherein, for example, it is in its lower end position where it can thus be immobilized. When the electric motor is turned on, it will heat up because of the extreme load, and the thermal safety system will be actuated. The driven component can also be damaged in this case as well.